Coiled tubing is a technology that has been expanding its range of application since its introduction to the oil industry in the 1960's. Its ability to pass through completion tubulars and the wide array of tools and technologies that can be used in conjunction with it make it a very versatile technology.
Typical coiled tubing apparatus includes surface pumping facilities, a coiled tubing string mounted on a reel, a method to convey the coiled tubing into and out of the wellbore, such as an injector head or the like, and surface control apparatus at the wellhead. Coiled tubing has been utilized for performing well treatment and/or well intervention operations in existing wellbores such as, but not limited to, hydraulic fracturing, matrix acidizing, milling, perforating, coiled tubing drilling, and the like.
In the oilfield, the length of downhole tools is often dependent on what function they are to perform, where additional functions typically require additional length. As more and more sophisticated functions are performed down hole, these tools have grown in length to the point where installing them in the well bore has become a significant challenge in the face of maintaining well control while this is performed. The process of placing tools into the well bore is referred to as deployment.
In spooled conveyance services such as coiled tubing, wireline, and slickline, downhole tools need to be transferred from the reel to inside the well bore. This transfer may be accomplished using a long riser with the conveyance attached to the top of the long riser. In this method, the tools are either pulled into the bottom of this riser, or are assembled into it. The riser is then attached to the well, is pressure tested, then the tools are run into the well after a successful test. In some cases, an ‘easier to run’ service is utilized to place the tools in the well, followed by a ‘harder to run’ service to perform the running in hole. In such cases, the downhole tools are provided with an additional part known as a deployment bar. This deployment bar is intended to provide a surface against which the blowout preventers (BOPs) can both grip and seal. In the case where the ‘harder to run’ service is coiled tubing, wireline or slickline may be used to pre-place the tools in the coiled tubing BOP. The deployment bar used will be selected to have a diameter substantially equal to the coiled tubing diameter. As part of the contingency plans, it is possible to close the master valves of the BOP. In order to do this while the downhole tools are hanging in the BOPs, and without opening the well to atmosphere (thereby creating a blowout), the deployment bar is capable of being sheared by the shear ram in the BOP. Once this is done, the slip and pipe rams can be opened and the tool dropped into the well.
Present positioning systems have limitations in positioning accuracy, particularly after having made large moves (like in and out of a well). In order to accommodate this, deployment bars are commonly made twice as long as the actual length required to clear all the pipe rams. Pulling the conveyance means up against its upper sealing means (stripper or packer) is used to re-locate, reducing the positioning issues. However, tagging parts implies a significant risk of pulling the conveyance means out of its attachment point. Further, positioning the deployment bar section accurately can range from difficult to extremely difficult, as it is very difficult to make precise moves with coiled tubing.
It remains desirable to provide improvements in oilfield surface equipment and/or downhole assemblies such as, but not limited to, methods and/or systems for deploying coiled tubing into wellbores.